lU BACTERIA AND FERMENTATION 



the warmth of the weather, fermentation is completed by the break- 

 ing away of the " shore " or " shive " (the woody core) from the flax 

 fibres. This decomposition and eventual breaking-down is due to 

 bacteria, which, under favourable circumstances, multiply rapidly 

 and set up the decomposition of the pectin resinous substance. 

 Winogradsky, in 1895, proved that the process was due to a large 

 bacillus (10-15 /x long, 1 jx broad). It is an anaerobe, growing not 

 in gelatine, but in the presence of nitrogenous food will ferment 

 saccharose, lactose, and starch. 



A precisely similar process is used in the preparation of jute and 

 hemp. The former is of course used in various fabric industries, the 

 chief centre of such manufactures being at Dundee. Jute fibre is 

 obtained from the bark of at least two species of plants allied to the 

 lime-tree order. The fibre, which is the inner bark, is separated from 

 the stem by retting, either in rivers or tanks. The retting lasts for 

 different periods, from two days to three weeks, and when the 

 cementing substance between the fibres and the stem is sufficiently 

 decomposed to allow of it, the jute fibre is separated, and may be 

 woven into sacking, carpets, curtains, etc. It is said that many of 

 the brightly-dyed prayer-carpets used in the East by Moslems are 

 made of this material in Dundee, and exported. Hemp also is 

 cultivated, in Poland and European Eussia for the sake of its fibre, 

 which is used for sail-cloth and other coarse material. This fibre is 

 also separated by retting. Another example of the same putrefactive 

 process is the preparation of cocoanut fibre for matting, etc. Some- 

 times retting for as long as twelve months is necessary to separate 

 the fibres from the unripe husk of the cocoanut. Sponges are cleared 

 in much the same manner by the putrefaction and softening of the 

 organic matter in their interstices, set up by micro-organisms. The 

 preparation of indigo from the indigo plant is brought about by a 

 special bacterium found on the leaves. If the leaves are sterilised 

 no fermentation occurs, and no indigo is formed. If, however, some 

 of the specific bacteria are added to the mass, the fermentation soon 

 begins, and the blue colour of the indigo makes its appearance. In 

 the treatment of ox-hides for the production of certain kinds of 

 leather the first object of the tanner is to clean and soften the hide, 

 which is accomplished by washing. The unhairing and removal of 

 the scarf-skin is the next operation, and this is achieved in America 

 by "sweating" the hides, or artificially heating them till incipient 

 putrefactive fermentation is set up by means of bacteria. Even in 

 the subsequent tanning bacteria probably play an important part. 

 But little is known at present of their work in this respect. 



In the production of tobacco, the leaves, when gathered, are allowed 

 to become somewhat withered, and are then arranged in moderate- 

 sized heaps, where they undergo a so-called " sweating," after which 



